Download Abstract: Eperythrozoonosis is a zoonosis transmitted from animals

Abstract:
Eperythrozoonosis is a zoonosis transmitted from animals to humans. It is caused by
Eperythrozoon, Which was divided into Rickettsia In Bergey's Manual, but it’s generally
considered to be part of mycoplasma according to 16sRNA sequence. Eperythrozoon is a
parasitic bacteria that invades erythrocytes, plasma, and bone marrow. It has high infection
rate and can cause varying degrees of damage. The more serious symptoms appear when more
than 60% of total erythrocytes are infected. It’s the first case report of infective endocarditis
caused by Eperythrozoon. The gold standard for diagnosis is the blood smear, It should be
considered in the cases of a fever of unknown origin that does not improve with empiric
antibiotic therapy as well as endocarditis with negative blood cultures.
Key words: Eperythrozoonosis, Eperythrozoon, Infective Endocarditis, Blood smear
Introduction
Infective endocarditis (IE) is the disease which has long term therapy and high cost, and
its’clinical diagnosis is relatively difficult. Cases of IE associated with negative blood culture up
to 31% of all endocarditis cases(1), and there is not yet report of Eperythrozoon in the present
pathogens related to endocarditis in China, not only is it largely because the deficiency of the
current detection methods, but it's also because of our insufficient clinical cognition.
Eperythrozoonosis was a zoonosis in many kind of animals, which parasite on erythrocytes,
plasma and marrow. Formerly, Eperythrozoon was classified as the rickettsial agent, recently
phylogenetic analysis of 16S rRNA gene showed that Eperythrozoon was closely related to
mycoplasma (Haemotrophic Mycoplasma)(2, 3). Blood smear examination was the mainly
method of diagnosis. It confirmed hemoplasma infection in humans showing fever, malaise,
drowsiness, splenohepatomegalia, decrease of red cell, hemoglobin and platelet, increasing of
bilirubin.
1. Case Report:
A 37-year-old woman with no significant past medical history presented to an outside hospital
with a 30 day history of remittent fever that gradually worsened during the first week. The
fever would fluctuate daily, rising as high as 41 degrees Celsius and decreasing to afebrile levels
without any medical intervention. She also reported chills and progressive weakness. She has
no previous history of heart disease. Six months earlier, she had eaten roasted lamb. Thirty
days ago, she spent one week in Hainan, China’s only tropical province, where she ate raw
seafood.
Laboratory investigations revealed an initial hemoglobin of 14 g/dL that decreased to 10.7
g/dL(normal: 11-15g/dL) after one month, WBC ranged from 3.3-4.9 x109/L(normal: 3.5-10
x109/L) with normal neutrophil and lymphocyte counts. ESR and CRP were mildly elevated at
46-51mm/hr (normal: 1-15 mm/hr) and 8.7-18.4mg/L(normal: 0-5 mg/L) respectively. T-Spot
test, antinuclear antibodies, viral antibody panel (Coxsackie, Epstein-Barr, Cytomegalovirus,
Herpes), Widal’s reaction, blood smear for malarial parasites, agglutination test for brucellosis
were all negative. Thyroid function tests, urine dipstick, ECG, and chest x-ray were
unremarkable.
At the outside hospital, the patient completed a four day course of amoxicillin/clavulanic acid,
five days of levofloxacin, three days of ceftriaxone and three days of artemisinin. Despite this
wide variety of antibiotics, the patient’s symptoms did not improve and was then transferred to
our hospital. All antibiotic treatment was then discontinued for seven days to rule out druginduced fever. Three sets of blood cultures post-antibiotic therapy showed no growth(4), yet
the patient continued to have a fever. A transthoracic echocardiogram performed about 20
days after onset of symptoms revealed a 0.97 x 0.65 cm vegetation on the non-coronary aortic
cusp (Figure 1). The patient then completed a six day course of amoxicillin/clavulanic acid with
no improvement of her fever(5).
The final results from two separate blood smears sent to the CDC of Hangzhou were then
obtained and were positive for Eperythrozoon (Figure 2). The patient was diagnosed with
Eperythrozoon endocarditis according to the Modified Duke criteria(5). Combined with
the treatment of endocarditis and Eperythrozoonosis respective, She was started on oral
minocycline 200mg daily for six weeks(5, 6). Her fever and weakness rapidly resolved within
the first 3 days of treatment and blood smears were negative for Eperythrozoon after antibiotic
therapy. A follow up transthoracic echocardiogram at six months revealed that the vegetation
became smaller in size and more stable. The patient remained afebrile and her hemoglobin
normalized.
2. Discussion:
Eperythrozoonosis is a zoonosis transmitted from animals to humans. More than 30 countries
worldwide, mainly China, have reported the disease in sheep, cattle, pigs, humans, etc. Patients
with Eperythrozoonosis and animals carriers of Eperythrozoon are the sources of this infectious
disease. The infection rates vary from 0 to 97% in China, and the incidence rate is significantly
higher in the summer and autumn compared to winter and spring(7). Survey data from the
Hangzhou CDC showed that the average infection rate of Hangzhou was 9.31%, of 580 people
including controls, meat processing workers, slaughter operators, veterinarians, farm workers.
And further found that it has significant difference in the infection rates of those wash their
hands or not after contact with animal fur, feces, raw meat, etc. And it also has significant
difference in the infection rates of using antibacterial soap to wash hands or not.
Eperythrozoon is a parasitic bacteria that invades erythrocytes, plasma, and bone marrow. They
are diversiform and mostly spherical, fusiform and short rod. The clinical manifestations of
eperythrozoonosis vary from asymptomatic subclinical infection to fever, weakness, scleral
icterus, and anemia depending on the ratio of infected erythrocytes. The more serious
symptoms appear when more than 60% of total erythrocytes are infected(8). Similar to malaria,
Eperythrozoonosis typically manifests as a remittent fever. It can be difficult to identify since its
nonspecific clinical signs belong in a wide differential diagnosis that includes influenza, malaria,
and anemia. The gold standard for diagnosis is the blood smear; DNA testing continues to be
imprecise due to incomplete knowledge of the gene sequence for Eperythrozoon(9), and the
hemoplasmas have highly dynamic genomes, and the lack of standards regarding genus
circumscription, etc. There is still no correct classification of these organisms. Therefore, a
blood smear should be considered in the cases of a fever of unknown origin that does not
improve with empiric antibiotic therapy as well as endocarditis with negative blood cultures(1).
It has high infection rate and can cause varying degrees of damage. And no one had reported
Eperythrozoonosis case involving the endocardium before this in China.
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